With the rapid proliferation of livestream e-commerce, hosts’ trust has become a major factor shaping consumers’ online purchase intentions. In real-time and highly interactive livestream settings, consumers rely heavily on hosts’ presentations and recommendations to obtain product information and reduce uncertainty, yet the ways in which hosts’ trust influences their purchase decisions remain insufficiently integrated. This paper adopts a qualitative, theory-building approach based on an extensive review of prior research and analysis of illustrative livestream cases to explore the impact of livestream e-commerce hosts’ trust on consumers’ online purchase intentions. The study takes a holistic view of hosts’ trust and examines its role in consumers’ information processing, risk evaluation, and emotional experience, analyzing how trust strengthens confidence in products and the transaction environment, lowers perceived risk, enhances shopping enjoyment and involvement, and thereby promotes both impulsive and planned purchases. The findings show that higher levels of hosts’ trust not only increase consumers’ immediate willingness to place orders but also foster ongoing attention and repeat purchase tendencies. The paper argues that systematically cultivating and maintaining hosts’ trust is a key pathway for platforms and merchants to enhance consumer engagement, build long-term relationships, and support the sustainable development of livestream e-commerce.